The invention relates to improvements in methods for making plastic film bags having reclosable fasteners thereon, and particularly of the type having opposed interlocking rib and groove elements on the confronting top edges of the bags.
In the manufacture of bags of this type, continual efforts are being made to increase the speed of production output to thereby effect a saving in cost of the individual bags. There are factors which limit the speed of extrusion of the film and speed of joining of profiles so that the present concept embodies manufacturing simultaneously a plurality of bags in a unique manner so that actually, material for making four bags with each cross-sealing operation is produced simultaneously in a single tubular extrusion film.
Attempts to make multiple bags in a single extrusion operation encounter the problems of controlling the film and controlling the profiles. The profiles are joined before the film is wound or spooled in order to avoid the risk of not knowing whether or not acceptable interlocking profiles have been provided and in order to complete the continuous strip in a form which is suitable for storage without deforming the profiles or damaging the film adjacent the profiles. Methods heretofore have been employed wherein tubular film has been formed and folded in such a way so as to simultaneously make dual bags with each cross-sealing operation. However, a feature of the present invention is to provide a method and mechanism for making a double double tube wherein material for four bags is formed. The difficulty in forming a double double tube is to handle the large amount of film emanating from the extruder, collapsing the bubble of the film so that the profiles are aligned and joined and handled in such a manner so that usable strips of profile film are provided which can be formed into four bags. The handling of such a tube creates problems in where the tube is to be slit, which profiles are to be joined to each other, and the collapsing of the bubble in such a manner that a fold mark is formed where the natural fold of the eventual bag will occur.
It is accordingly an object of the present invention to provide an improved method for forming a unique tubing which is capable of being converted into four reclosable bags at one time by a single cross-cutting and sealing arrangement. More particularly, the method of the invention provides double double profile film sets or in other words, two sets of double profile film.
A further object of the invention is to provide a unique manner of slitting and folding and joining profiles in a tubing so that strips of double profile film for conversion into two sets of double bag film strips are formed.
A feature of the present invention is the formation of a continuous tube of film with eight profiles on the inner surface, and finding a satisfactory way of joining said profiles so as to form profile film strips that can be readily converted into sets of reclosable bags. One unsatisfactory manner of approaching the problem is to roll the tube into a spool after aligning the profiles, but not joining them, so that the tube is folded between profiles and then separating and rejoining the tube sections later at the bag machine. This situation creates the problem of not knowing whether or not the profiles are satisfactory until much later.
Another alternative unsatisfactory solution to handling the tube is to slit the tube into two sections which would have to be joined onto themselves and spooled.
A feature of the invention is the making of a quadruple profile tube which is then divided into two sets of double profile film wherein the profile from one of the film sections is folded into the other film sections and vice-versa. In this manner, production output can be increased substantially since two double profile films for conversion into reclosable bags are provided from one quadruple profile tube.
Other objects, advantages and features, as well as equivalent methods and apparatuses which are intended to be covered herein, will become more apparent from the teachings of the present invention in connection with the disclosure of the preferred embodiment thereof in the specification, claims, and drawings, in which: